INTERCOMPARISON OF VACUUM STANDARDS OF COUNTRIES WITHIN THE EUROPEAN-COMMUNITY IN THE RANGE 8X10-5 TO 8X10-2 PA

A comparison of the vacuum standard maintained by four laboratories within the European Community has been made in the pressure range 8 multiplied by 10** minus **5Pa to 8 multiplied by 10** minus **2Pa using a JHP high pressure ionization gage. Three gages were circulated around the participating laboratories, each laboratory carefully following a detailed procedure for the preparation and operation of the gage so as to minimize random variations in the sensitivity coefficient of the gage. The gages were calibrated up to nine times at each pressure by all the laboratories, the measurements in each laboratory taking place over a period of three days. The results indicate that when the three JHP gages were used in the carefully controlled manner described in this paper, the ionization gage coefficient did not change from its initial value by more than plus or minus 1. 7% over an 18 month period.